Have 3 or more pad holders, this depends on how many rucking units you wish to have and how many players you have at training - but work hard to keep every player busy and active. The 3 pad holder should be about 5 meters back from the rucking units, and they should be holding the pads safely. Players should work in groups of 2, and there will be 1 scrum half. Only one ball is needed as the scrum half will move the ball from unit to unit. Get the players moving quickly, and tell the players the following.... One player carries the ball into contact and presents the ball. The other player provides covers and time for the scrum half to move the ball to the next unit. The scrum half should move the ball from unit to unit, and the units/pads should reposition themselves for the next line of attacks. Keep the action going, and don't forget to change the players on the pads.